1. Field of the Invention
The present invention relates to an LED drive device which is incorporated in an LED illuminating device employing a plurality of LEDs (Light Emitting Diodes); an LED backlighting device employing the LED illuminating device; an image displaying unit employing the LED backlighting device to display images, etc., and suitably operates especially in the event of an LED fault. The present invention also relates to an LED illuminating device with such LED drive device incorporated therein.
2. Description of the Related Art
Heretofore, with respect to an LED drive device for driving a plurality of LEDs, e.g., Japanese unexamined patent application publication No. 2004-126082 (hereinafter called patent document 1), for example, discloses a technique in which it is detected whether each LED making up an LED sign lamp is faulty or not and then the number of faulty LEDs is counted and if the number of the faulty LEDs is not less than a preset value, an informing device informs such faulty condition to prompt replacement of the LED sign lamp. This technique has been proposed in terms of the fact that it is rather uneconomical to replace or repair the illuminating unit every time only one or several LEDs of a large number of LEDs thereof fail to operate properly, because the illuminating performance as an illuminating unit is hardly impaired in such case. Further, Japanese unexamined patent application publication No. 2007-165161 (hereinafter called patent document 2) discloses a technique in which when any one or more LEDs have developed open faults in a row of series-connected LEDs supplied with a source voltage, zener diodes, e.g., which are connected in parallel with one or a plurality of the LEDs and thereby act as a current bypass means, are allowed to conduct to prevent the whole of the LEDs from being turned off.